The operating principle of magnetic brake-dampers is based on interaction of the magnetic flux created by a permanent magnet with the electric current induced by this flux in the moving element of an instrument. The prior art magnetic brake-dampers do create the necessary braking and damping moments. However, the pronounced magnetic leakage from the surface of the employed permanent magnets sharply reduces the working magnetic flux creating a breaking or damping moment. This results in high consumption of magnetic materials for permanent magnets and also results in magnetic brake-dampers becoming quite cumbersome. The increasingly stringent requirements for the output parameters of magnetic brake-dampers and greater output of instruments in which they are used necessitate optimized designs characterized by smaller sizes and lower magnetic material consumption.
There is known a magnetic brake-damper of an electric measuring instrument (cf. A.M. Ilyukovich, Electric Meters, "Gosenergoizdat" Publishers, 1963, p. 314/in Russian/), comprising a dipole cylindrical permanent magnet. One of the end faces of the cylinder has a diametral slot, and the resulting projections on either side thereof serve as magnet poles. There is also provided a flat magnetic core arranged above the poles of the permanent magnet with a gap therebetween, accommodating part of the electric meter disc.
The magnetic flux is thermally compensated by a plate of a thermomagnetic material, placed between the poles of the permanent magnet.
The above magnetic brake-damper has an extended, as compared to the pole area, side surface normal to the plane of the disc, resulting in a large leakage flux not contributing to creating a braking moment, which necessitates a large magnet to create the required braking moment.
Also known is a magnetic brake-damper of an electric measuring instrument, comprising two similarly magnetized permanent magnets with opposite poles, arranged one above the other and forming a gap accommodating part of the moving element of the instrument (cf. A.M. Ilyukovich, Electric Meters, "Gosenergoizdat" Publishers, 1963, p. 316/in Russian/).
In this magnetic brake-damper, used as a means for closing the magnetic flux, there is included a cylindrical permanent magnet with a diametral slot made on one of its end faces. Both magnets are magnetized along an arc in the same direction and are normal to the moving element plane. The magnetic flux is thermally compensated by means of a plate of a thermomagnetic material, disposed between the magnet poles.
The configurational complexity of the magnets with curvilinear magnetization and the extended area of their side surfaces, responsible for a large leakage flux which does not participate in creating a braking moment, increase the size and magnetic material consumption of said magnetic brake-damper.